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From "Rui Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-8518) Compile time skew join optimization returns duplicated results
Date Mon, 20 Oct 2014 09:33:33 GMT

    [ https://issues.apache.org/jira/browse/HIVE-8518?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14176755#comment-14176755
] 

Rui Li commented on HIVE-8518:
------------------------------

cc [~xuefuz]

> Compile time skew join optimization returns duplicated results
> --------------------------------------------------------------
>
>                 Key: HIVE-8518
>                 URL: https://issues.apache.org/jira/browse/HIVE-8518
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Rui Li
>            Assignee: Rui Li
>         Attachments: HIVE-8518.1.patch
>
>
> Compile time skew join optimization clones the join operator tree and unions the results.
> The problem here is that we don't properly insert the predicate for the cloned join (relying
on an assert statement).
> To reproduce the issue, run the simple query:
> {code}select * from tbl1 join tbl2 on tbl1.key=tbl2.key;{code}
> And suppose there's some skew in tbl1 (specify skew with CREATE or ALTER statement).
> Duplicated results will be returned if you set hive.optimize.skewjoin.compiletime=true.



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